Selective CW filter with 4 crystal IF filter and audio band pass filter

7 to 12 volt supply supporting;

4.5 to 5 Watt transmitter output on all bands (with 12 volt supply)

2.5 watts output typical with 9 volt supply

50 ma no signal receive current

680 ma maximum transmit current at 12 volts

Small size, 12.5cm wide, 6.8cm deep, 2.5cm tall

Light weight, 178G.

This is a SOTA radio.

This kit was released 2011 so lucky to get my hands on one (Thanks Tyler and Bill). You can purchase an assembled similar radio being a LNR MTR4B (80,40,30 & 20) at 400US$ + freight. Given the declining AUD (thanks mining why does the need for foreign owned enities to profit override my desire to play radio ?) it really has not been high on my list to purchase one. I jumped at the kit. This device supports 80m.

Have a mate in the US (Thanks Jason) and he was happy to receive and send on to me so ended up landing here at around $400AUD inc freight.

This is a part of the quest to reduct weight so as to pickup some of the more challenging summits. Whilst are not a long walk they will be a big effort given the terrain and conditions. This device will keep the radio and antenna equipment well under 1Kg and support 5 bands be it CW only.

Reluctant to go out without 80m. For the chasers as much as to ensure enough contacts to qualify. Not having issues getting CW contacts these days.

Had spent the morning soldering copper tubing for fire sprinkler system. This is using the gas torch, liquid flux and 3mm solder. The afternoon was to be different. Once it started to rain (the geese were happy) I decided to come in and get out of the mud and cook up a radio.

This kit contains SMD components. Previous build of SMD based device was a KD1JV MTR v2. This went well with the only real issue being as a result of losing a component and replacing with the wrong type.During the build, you have to choose between 17m or 15m. I will go for 15m.

Day One

Having read the manual and check the parts it was time to start assembly. This is not a task to rush into but rather progress in an orderly manner.

First step is to add the IC’s. Decided to hand solder these as a single task as the idea of placing all the semiconductors, capacitors and resistors then melting the solder in one sitting did not sound like a good idea.

At end of day one I had the IC’s on ready to inspect. Completed page 15 of the manual.

Day Two. Testing the rework device.

Was not filled with desire to start heating up the board yesterday. Decided to verify the hot air soldering process before going forward. Using Solder Paste from Jaycar which has the Chemtools ID on it. Found the spec sheet on Chemtools website.

Yes using leaded solder. Have had trouble with using unleaded solder and think by now I have enough lead in my system given the paint used when a kid and the years of soldering not to get too worried about it.

Didn’t trust the 852d+ soldering rework station so checked the temp and tested with an old board from the shed. Yes the display was out so experimented until in the range and able to take caps off the S3 board and solder them back on in a timely manner. All good.

So think I’ve procrastinated enough so time to commit to melting solder, tomorrow caps ….

Day Three. Check and Check again.

Zoomed in on some components with a 2MP USB microscope from eBay checking.

Upgraded the lights above the table but basically my eyes are not what they use to be so need such a tool. Not the absolute answer but these microscopes are worth the $A30.

Mixed results. The microscope stand had to be extended to get a good view. It did expose issues (surprising number of joints that were missed) and they were addressed. Once checked and addressed went back with magnifying glass and checked again. If this was left it would manifest as failure in the field so keen to fix now.

Day Four. Capacitors Bottom Side.

Capacitors went on well. So will check the board again to be sure.

Day Five. Through Hole Components.

Not consecutive process as well work and we went Wuthering Saturday. Checkout the video, thats us in the red to the left !

The SMD parts went well. Very happy with the result. Working through the through hole components now.

Wet and windy weekend to was able to continue work on assembly Sunday. I have been following the instructions carefully as aware may not get such a kit again and that components may not be available should I loose or break some.

Adding the Low Pass filters (Page 20 in the assembly manual), which states that “These all go onto the Bottom Side of the board” whilst the picture on same page shows C73,C74 and C75 mounted from the top. I soldered C74 was per the instructions and whilst checking noted the discrepancy created by the picture. Removed C74 and placed in on the top of the board as per the picture. This caused conflict in my head and went checking out pictures on the web and which show them mounted on the the bottom.

See no reason to tempt fate de-soldering and moving C74 again so leaving as is on the top. Also have enlarged the hole to support a BNC connector for the antenna. Files the hole so it was slightly higher so as avoid the board. As you can from a dry run it will fit without causing grief.

Working through the toroids now, again carefully and without time constrains.

Day Six. Final Assembly.

Well actually 10 days in total but have to go to work and other things….

After winding and installing the toroids its a case of assembling the hardware and connectors.

She did not come up on the first test and this was quickly traced back to a faulty 9V battery connection. Found another in my sons junk box and away it went.

From here it worked as described. The DDS came up on 10Mhz exactly.

Outputting 2w on the 40 – 15M 9V with 80M around half that. I took note of the torrid winding (loose for even and tight for odd) but there is not a lot of room to move for L12 & L14.

Connected to the home antenna and turned the receive to peak noise.

The unit is operating so ready to take out onto a summit.

I see no value in disassembling and trying to refine the windings on 80M. Ok yes did chase this device for 80M but its a fall back frequency. Let’s get out on a summit and see how it works before playing with the number of turns.